Challenges and Uncertainties in Reservoir Geomechanical Characterization for Horizontal Well Planning in Deep Unconventional Reservoirs in North Kuwait Fields

摘要

Appraisal of deep unconventional reservoirs through horizontal and high angle drilling campaign in North Kuwait Jurassic Fields requires the knowledge of in-situ stress regime, particularly orientation and magnitudes, to provide optimized solution for safe drilling and completion designs. A comprehensive geomechanical analysis i.e. broader geomechanical framework of the overburden section and a detailed geomechanical characterization at the reservoir targets for drainhole section, for the best possible orientations and stability parameters during drilling and completion is a key for the fields with sparse vertical and deviated wells control and short production history. This paper outlines the integrated approach adopted and discusses the challenges and uncertainties in the reservoir geomechanical modelling and characterization. Interpretation of caliper data and borehole images are used to determine the stress direction for vertical and near vertical wells. The minimum stress and maximum stress directions are established from orientation of breakouts, maximum ovality from calipers and from orientation of drilling induced fractures respectively. Comprehensive integrated geomechanical properties for all the formations units of the unconventional reservoir sequence are computed. The results indicate that the stress regime varies from ‘strike-slip to inverse’ and are found being formation dependent with associated intrinsic rock mechanical properties and spatial position of the wells under study. 1-D mechanical earth model (MEM) and WBS analysis are also done to calibrate the results. The stress magnitudes are constrained using data frac job results. Results of study and knowledge of stress direction and regime are used for the planning and defining horizontal well trajectories optimization as well as in estimating mud weight window for safe drilling and optimizing completion designs.